Groundwater quality assessment using data clustering based on hybrid Bayesian networks

Bayesian networks (BNs) have become a standard in the field of Artificial Intelligence as a means of dealing with uncertainty and risk modelling. In recent years, there has been particular interest in the simultaneous use of continuous and discrete domains, obviating the need for discretization, using so-called hybrid BNs. In these hybrid environments, Mixtures of Truncated Exponentials (MTEs) provide a suitable solution for working without any restriction. The objective of this study is the assessment of groundwater quality through the design and application of a probabilistic clustering, based on hybrid Bayesian networks with MTEs. Firstly, the results obtained allows the differentiation of three groups of sampling points, indicating three different classes of groundwater quality. Secondly, the probability that a sampling point belongs to each cluster allows the uncertainty in the clusters to be assessed, as well as the risks associated in terms of water quality management. The methodology developed could be applied to other fields in environmental sciences.     

A high-resolution stellar library for evolutionary population synthesis

We present a library of 1654 high-resolution stellar spectra, with a sampling of 0.3 Å and covering the wavelength range from 3000 to 7000 Å. The library was computed with the latest improvements in stellar atmospheres, incorporating non-local thermodynamic equilibrium (non-LTE) line-blanketed models for hot, massive  ( T _eff≥ 27 500 K)  and line-blanketed models for cool  (3000 ≤ T _eff≤ 4500 K)  stars. The total coverage of the grid is  3000 K ≤ T _eff≤ 55 000 K  and  −0.5 ≤ log g ≤ 5.5  , for four chemical abundance values: twice solar, solar, half solar and 1/10 solar. Evolutionary synthesis models using this library are presented in a companion paper. We tested the general behaviour of the library by calculating and comparing equivalent widths of numerous H and He  i lines, and some of the commonly used metallic indices. We also compared the library with the empirical libraries STELIB and Indo-US. The full set of the synthetic stellar spectra is available from our websites ( http://www.iaa.csic.es/~rosa and http://www.astro.iag.usp.br/~lucimara/library.htm ).     

Identification of hydrogeochemical processes in a volcano-sedimentary aquifer of Ciénega de Chapala in Michoacán,Mexico

The present study characterized the hydrogeochemical processes of the aquifer of Ciénega de Chapala in Michoacán, Mexico. The dominant water families contained bicarbonate magnesium and sodium. In the region, water infiltrates into a fractured volcanic environment exposed in the surrounding mountains and is transmitted to the volcano-sedimentary units of the ciénega, where silicate alteration and ion exchange processes occur in the clays of the subsoil. The Gibb diagrams confirm that the main evolutionary processes in the aquifer are rock-water interactions in the local flow and evaporation in the intermediate and regional flows. The molar ratios of HCO₃/Na and Ca/Na are congruent with the type of volcano-sedimentary environment present in the area. Ternary mixing processes associated with three end members were also identified and were related to the flow systems in the area. The local flow contributes 77% of water to the system, and the intermediate and regional flows contribute 16% and 7%, respectively.     

Rapid characterisation of the extremely large landslide threatening the Rules Reservoir (Southern Spain)

Landslides - When an active landslide is first identified in an artificial reservoir, a comprehensive study has to be quickly conducted to analyse the possible hazard that it may represent to such...     

Bacterial accumulation by Branchiomma luctuosum (Annelida: Polychaeta): a tool for biomonitoring marine systems and restoring polluted waters

In this study, we examined the bacterial accumulation in the filter feeder polychaete Branchiomma luctuosumGrube (Sabellidae). Analyses were performed on worm homogenates from 'unstarved' and 'starved' individuals, and seawater from the same sampling site (Gulf of Taranto, Western Mediterranean, Italy). Densities of culturable heterotrophic bacteria (22 degrees C), total culturable bacteria at 37 degrees C and halophilic vibrios at 22 and 35 degrees C were measured on Marine Agar 2216, Plate Count Agar and thiosulphate-citrate-bile-salt-agar (TCBS) plus 2% NaCl, respectively. Total and faecal coliforms as well as faecal streptococci were determined by the Most Probable Number method. Results showed that B. luctuosum is able to accumulate all the considered six microbiological groups with a higher efficiency for autochthonous bacteria. The analysis also indicated that bacterial groups differ in their resistance to digestion by B. luctuosum. Our data suggest the potential role of B. luctuosum as an useful bioindicator to assess low levels of microbiological water pollution as well as bioremediator of microbial polluted waters.